1. Field of the Invention
The present invention is generally directed to a photoelectric measuring apparatus, and more particularly, an apparatus creating measurement and reference signals by components formed on an integrated optical circuit.
2. Description of the Prior Art
A wide variety of photoelectric measuring devices exist, however, they all suffer from disadvantages the present invention eliminates.
Typically, an integrated optical circuit creates a measuring signal and a reference signal, the reference signal being used to determine the direction of movement while the measurement signal determines the amount of movement. In an article by Ura, et al. "Integrated-Optic Interferometer Position Sensor," Journal of Light-wave Technology, Vol. 7, No. 2, February 1989, an integrated optical interferometer is disclosed. Part of a beam emitted from a laser is diffracted and strikes a moving mirror which reflects the beam back to the waveguide thereby forming signal waves. The other part of the beam emitted from the laser strikes a Bragg reflector. The Bragg reflector focuses the reflected beams into photodiodes to create reference waves. The signal and reference waves interfere and are detected by the photodiodes so that displacement of the moving mirror is detected through periodic modulation of the output photo currents.
German reference DE-C2 36 30 887 discloses a measuring arrangement on a substrate wherein a waveguide is connected with a laser. At one end of the waveguide there is either a coupling-in or decoupling grid for the measuring beam. By means of a coupler there is obtained from the measuring waveguide, a so-called reference waveguide which ends on a metallized edge of the substrate which forms a mirror for the reference waveguide. Such mirrors or Bragg reflectors are difficult to construct and produce in an integrated optical system. In addition, measuring arrangements that employ lenses are difficult to produce in an integrated optical system.
Accordingly, it is a primary object of the present invention to provide a measuring device that utilizes reflectors and lenses in an integrated optical system thus facilitating the construction of the device and reducing the size of the measuring device.
Another object of the present invention is to provide a measuring device that may be economically produced and easily adapted to various measuring requirements while operating free from interference.